It is common in the communications field to use cables containing up to 3000 or more pairs of conductors. These cables may be grease-filled or under air pressure to prevent moisture from reaching the individual wires within the cable, the effect of which would be to change the electrical properties of the wires or cause them to short out. It is the usual practice in the communications field to use large diameter pressurized cable near central office installations but, for reasons of economy, grease filled cable of smaller diameter are used in areas remote from a central office and closer to an individual user. At the transition splice between pressurized and grease filled cable a pressure block is required to prevent the pressurized air from entering the grease-filled cable and blowing out the grease. In such a situation, a plugging compound is used.
An encapsulating compound is needed when two non-pressurized cables, one or both of which may be grease filled, are to be spliced together. To prevent moisture from entering the splice, either the greasy conductors must be thoroughly cleaned, a time-consuming and expensive procedure in the field, or an encapsulating compound having high adhesion to greasy wires is required.
U.S. Pat. No. 4,102,716 discloses a polyurethane gel, which is an oil extended resin, that is useful as a filler for communication splices. This gel is of limited use with grease filled cable and is not suitable as a blocking or plugging compound due to its jelly-like consistency. U.S. Pat. No. 4,168,363 teaches a polyurethane blocking or splicing composition for repair of elastomeric cable jacket materials requiring a thickening agent, a liquid diluent, and filler materials in its formulation. The patentee claims good adhesion to clean elastomeric cable jacket material. BRD Offenlegungsschrift 28 47 387 discloses a tacky, elastic polyurethane-based filler for cable and insulated wire sealing that has a major polyester-polyether-polyol or polyester-polyol component, the diisocyanate component, to which no criticality as to type is disclosed, being a monomeric aryl, alkyl, or (ar)alkyl diisocyanate.
There exists a need in the art for a composition that will cure in situ under ambient conditions to provide a high modulus, high tensile strength filler composition having superior adhesion to greasy wires.